This study compares lithium carbonate to placebo in the treatment of Conduct Disorder in adolescents. This is an inpatient study for two weeks of experimental treatment. The specific aim is to test whether lithium is an effective treatment of this disorder for which no treatment has been proven effective. Conduct Disorder is a common disorder in adolescents, causes considerable discomfort and hardship to patients, their families, and to the community. There is suggestive evidence in adults, adolescents, and children that lithium is anti-aggressive, although the question has not been studied systematically in adolescents.